What is your frontend configuration?

We use the web GUI and Thunderbird 3.1 with Lighning (official version, without sogo connector)

Can you give us the content of your Apache configuration?

I uploaded the apache and the sogo configuration.

Something to try.

Try uninstalling and reinstalling (you can reinstall nightly or 2.0.2).

If you are using RedHat/Centos:

rpm -ve sope49-core sogo gnustep-base gnustep-filesystem gnustep-make libmemcached libobjc sope49-appserver sope49-cards sope49-core sope49-gdl1 sope49-gdl1-contentstore sope49-ldap sope49-mime sope49-sbjson sope49-xml sope49-gdl1-mysql

yum install sogo

I had this issue when I used "yum update" (not sure which exact package broke it though)

After a full reinstall process the service worked well with default configuration, but reloading the old configuration, freezed again. So I parsed the .GNUstepDefaults file, and found some keys not defined in the current documentation:
WOApplicationRedirectURL;
WOMessageUseUTF8;
WOParsersUseUTF8;
WOUseRelativeURLs;
Removing this entries the problem resolved, the GUI and Lightning are working now.
Thanks for your help.

WOApplicationRedirectURL should never be used anymore. IIRC, it causes segfault.

See my last comment. You should no longer use WOApplicationRedirectURL.